Onyx Company Prepared a Static Budget at the Beginning of the Month

Onyx Company prepared a static budget at the beginning of the month. It's the end of the month and the company is analyzing actual results versus budget using flexible budget methodology. Data are as follows:
Static budget: Sales volume: 1,000 units Price: $70 per unit
Variable expense: $32 per unit Fixed expenses: $37,500 per month
Operating income: $500
Actual results: Sales volume: 990 units Price: $74 per unit
Variable expense: $35 per unit Fixed expenses: $33,000 per month
Operating income: $5,610
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Based on the above data, how much was the flexible budget variance for sales revenue?

A) $5,490 U
B) $5,490 F
C) $3,960 U
D) $3,960 F